Ball valves have been used in a variety of industrial processes and in subterranean use such as a wellbore. These designs feature a plug or ball that turns 90 degrees between an open and a closed position usually between two sleeves that have end seals that abut the ball or the plug as the ball is turned by a manual or automatic actuator that is rotated in line with two opposed pivot pins that extend from the ball or plug and are otherwise retained by the valve housing. The actuator can be as simple as a handle or it can be a more complex assembly of a piston engaging a cage around the ball in a location offset from the pivot axis so that piston reciprocation turns the ball or the plug the required 90 degrees between the fully open and closed positions.
Usually the ball seals were resilient materials that had temperature service limits of around 100° C. Various specialty materials such as Teflon® were used to increase the temperature service limits. There were concerns with the safety of such valves to hold pressure in the event of a fire that destroyed the resilient seals. Some ball valve designs were advertised as safe in fires because they employed a variety of designs that could move a metal to metal seal against the ball as the resilient seal failed from excess temperature. Some designs along these lines are U.S. Pat. Nos. 4,509,546; 3,392,743; and 5,106,176. Metallic deformable seals have been used to seal annular spaces such as in packers used for zone isolation in a wellbore as illustrated in U.S. Pat. No. 6,896,049 or 7,316,271.
Some ball valve designs used an L-shaped metal seal and took advantage of stored potential energy in the shape to keep an end of it against the ball surface. In variation of that design differential pressure across the seal was used to physically advance a leg of the seal assembly by securing the leg to a piston that was biased by the differential pressure across the seal. These design variations can be seen in U.S. Pat. No. 4,147,327 entitled Metallic Seals for Ball Valves.
The present invention uses a metallic seal with multiple discrete seal locations with a shape in section that defines a single entry chamber so that pressure in the chamber enhances the seal. Rounded contact locations on the seal with the valve housing and the ball are preferred. The chamber inlet configuration acts to minimize undue deflection that may cause the chamber opening to close as well as addressing the provision of a support to reduce the chance of undesired plastic deformation of the metal seal. These and other aspects of the present invention will be more readily appreciated by those skilled in the art by a review of the description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined by the appended claims.